Systems other than air-water

For systems other than air—water vapor or for total system pressures different from 101.3 kPa (1 atm), humidity diagrams can be constmcted if basic phase-equihbria data are available. The simplest of these relations is Raoult s law, apphcable at small solute concentrations ... 

Work in the area of simultaneous heat and mass transfer has centered on the solution of equations such as 1—18 for cases where the stmcture and properties of a soHd phase must also be considered, as in drying (qv) or adsorption (qv), or where a chemical reaction takes place. Drying simulation (45—47) and drying of foods (48,49) have been particularly active subjects. In the adsorption area the separation of multicomponent fluid mixtures is influenced by comparative rates of diffusion and by interface temperatures (50,51). In the area of reactor studies there has been much interest in monolithic and honeycomb catalytic reactions (52,53) (see Exhaust control, industrial). Eor these kinds of appHcations psychrometric charts for systems other than air—water would be useful. The constmction of such has been considered (54). 

For systems other than air-water vapor, the value of h /k c, may differ appreciably from unity, and the wet-bulb and adiabatic-saturation temperatures are no longer equal. For these systems the psychrometric ratio may be obtained by determining h /k from heat- and mass-transfer an ogies such as the Chilton-Colburn analogy [Ind. Eng. Chem., 26, 1183 (1934)]. For low humidities this analogy gives... 

The calculation of conditions within a countercurrent column operating with a system other than air-water is carried out in a similar manner to that already described by... 

For systems other than air-water, testing is normally required. Now let s do two gas-liquid example problems. (Examples 10.13 and 10.14). 

The psychrometric chart can be used for a number of other purposes since it is really just a graphical means of presenting the mathematical relationships between the material and energy balances in the air/water vapor systems. It may be pointed out that psychrometric charts exist for systems other than air/water vapor. The charts may be drawn in different ways, but they usually include a basic temperature (dry bulb) and humidity (absolute humidity) set of coordinates (Fig. 1). Additional lines or parameters that are usually included are ... 

HUMIDITY CHARTS FOR SYSTEMS OTHER THAN AIR-WATER. A humidity chart may be constructed for any system at any desired total pressure. The data required are the vapor pressure and latent heat of vaporization of the condensable component as a function of temperature, the specific heats of pure gas and vapor, and the molecular weights of both components. If a chart on a mole basis is desired, all equations can easily be modified to the use of molal units. If a chart at a pressure other than 1 atm is wanted, obvious modificatioi in the above equations may be made. Charts for several common systems besides air-water have been published. ... 

The following procedure is recommended for predicting holdup for systems other than air-water. The average superficial velocity in the column is calculated allowing for the solvent vapor pressure and the average absolute pressure, and e for the air-water systems is predicted from Figure 7.11. Then the ratios of physical properties are used to adjust the value of e if the viscosity is about 1 cp or less (10 Pa-sec) ... 

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